Amino acids
L-Theanine
Calm · focus
Tea-derived amino acid; alpha-wave EEG activity, calm focus, attenuates caffeine jitters. Common dose 100–400 mg.
What L-Theanine does
L-Theanine is a non-protein amino acid concentrated in tea (especially shade-grown matcha and gyokuro). It crosses the blood-brain barrier and increases alpha-wave activity on EEG within ~30 minutes — the neural correlate of relaxed alertness. Its most reliable acute effect is attenuating the jitter and stress response from caffeine without reducing the alertness benefit; pairing 100 mg L-theanine with 50–100 mg caffeine has clinical-trial support for cognitive tasks under load. It's not a sedative.
Food sources of L-Theanine
Approximate L-Theanine content per serving. Whole-food intake counts toward your daily total alongside any supplemental dose.
| Food | Serving | L-Theanine |
|---|---|---|
| Matcha green tea | 1 cup | 20–45 mg |
| Brewed green tea | 1 cup | 8–25 mg |
| Brewed black tea | 1 cup | 5–15 mg |
| Brewed white tea | 1 cup | 5–15 mg |
Signs of L-Theanine deficiency
- ●Not an essential nutrient — no deficiency state
Who needs more L-Theanine
Groups and situations where L-Theanine requirements rise or status commonly runs low:
- ●Anyone using caffeine for performance who doesn't tolerate the jitter or anxiety component
- ●Pre-meeting / pre-presentation calm-focus protocols
- ●Sleep-onset support at 200–400 mg (modest evidence; works for some)
How L-Theanine appears on labels
Supplement labels list L-Theanine under several names depending on the chemical form used. Any of these on an ingredients panel counts toward your L-Theanine intake:
- l-theanine
- theanine
- suntheanine
Best supplements for L-Theanine
Top-scoring supplements in our catalog that list L-Theanine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Deep dive
For mechanism of action, dosing protocols, evidence grade, and interaction warnings on L-Theanine, see the full encyclopedia entry:
L-Theanine encyclopedia entry →Conditions where L-Theanine has evidence
L-Theanine appears on the supplement list for the following condition pages — each links to the full evidence summary, dose, and lifestyle context.
Research on L-Theanine
Peer-reviewed studies in our research database that reference L-Theanine. Each entry links to a detailed methodology review.
- Hidese S, Ogawa S, Ota M, et al., 2017 · Acta NeuropsychiatricaEffects of chronic l-theanine administration in patients with major depressive disorder: an open-label study
- Nobre AC, Rao A, Owen GN, 2008 · Asia Pacific Journal of Clinical NutritionL-theanine, a natural constituent in tea, and its effect on mental state
Guides covering L-Theanine
Long-form articles in our guide library that go deeper on L-Theanine — comparisons, protocols, and reviews.
Frequently asked questions
What is the daily target for L-Theanine?
What foods are highest in L-Theanine?
What is the best form of L-Theanine to supplement?
What are the signs of L-Theanine deficiency?
Who is most at risk for low L-Theanine?
Related amino acids
Track your full intake
Formulate's free web app aggregates L-Theanine (and ~40 other nutrients) across every supplement in your stack — flagging underdoses, overlaps, and upper-limit overshoots in one view.
Track your intake free →Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Targets and upper limits are general adult reference values; individual needs vary by age, sex, pregnancy status, and clinical context.